1. Technical Field
The present invention relates generally to attachment devices. More particularly, the present invention relates to snap-fit attachment devices for use to retain a flexible member between two spaced support components without additional attachment fasteners. Specifically, the present invention is directed to a snap mounted attachment means intended primarily for mounting the ends of a fluid actuated device between two spaced support components.
2. Background Information
Fluid actuated devices take many forms of which air springs are one type. Air springs consisting of a pair of spaced end members and an intervening flexible sleeve or bellows which forms an internal pressurized fluid chamber, have been used for many applications, such as mounting between spaced components of a vehicle for absorbing road shock, supporting parts of machines and equipment, such as presses on which shock forces are continually imparted, and for regulating and maintaining the spacing between two spaced components of various pieces of equipment. These air springs assume various configurations depending upon their particular application. Such air springs usually consist of one end member which is an end cap, with the other member being a piston. The piston usually has a conical outer surface over which a rolling lobe of the flexible bellows moves for affecting the damping of the vehicle or equipment on which the air spring is mounted.
Some examples of such prior art air springs are shown in U.S. Pat. Nos. 3,682,464, 4,506,910 and 4,718,560.
Heretofore, these air springs were attached to the spaced supporting members, and in particular to the spaced components of a vehicle, by various attachment bolts or fasteners which extend into the piston and end cap, such as shown in the above referenced patents. However, for certain applications, due to the limited space available for mounting the air springs within a vehicle and the inaccessibility of the air spring mounting supports or brackets, difficulties are encountered in reaching both ends of the air spring for securing the same to the support members by usual attachment bolts. Also, the use of separate attachment bolts, even if access is possible, requires additional equipment and manpower for securing the bolts to the air springs. Moreover, the oxidation of the metal fasteners create potential failure problems for the air spring assembly. Also employed in the prior art, is the blind hole bolt attachment, as explained in more detail in the specification to follow.
Therefore, the need exists for an improved attachment device for mounting a first member such as an end cap of an air spring, onto a supporting structure, and in particular for mounting the end cap and piston of an air spring onto spaced supports within a vehicle without separate attachment bolts or fasteners. Various types of snap mounting attachment devices have been developed in the past for various applications, examples of which are shown in the following patents.
U.S. Pat. No. 3,169,292 discloses a snap fastener which includes a stud element having beveled surfaces which join a neck and a large diameter surface. The beveled surface will facilitate the removal of the stud from the socket opening. A bulbous head has a curved cam surface which facilitates attachment of the fastener to the socket.
U.S. Pat. No. 3,415,155 discloses a bushing formed of plastic having resilient ears which project radially outwardly from a main body of the bushing adjacent one end and has a radial annular shoulder on the bushing adjacent the other end which is snap-fitted through a hole in a plate when inserted through the hole, with the ears remaining on the exterior of the plate, after which a pin is snap-fitted into the bushing.
U.S. Pat. No. 3,476,008 discloses a fastener having a shoulder portion which facilitates secure attachment of the fastener. The stud fastener has a disc shaped head and legs which have shoulders which extend through a support aperture to engage edges of the aperture and attach the fastener to the support.
U.S. Pat. No. 3,818,729 discloses a brake yoke rod attachment for an automatic washer which has a plurality of segments which have frustaconical surfaces which are formed as angled cam surfaces to facilitate installation and removal of the attachment on the washer.
U.S. Pat. No. 4,012,155 discloses a snap lock connector in which a male member of the connector has leading and camming surfaces which correspond to leading and camming surfaces of a female member. These camming surfaces facilitate the installation and withdrawal of the male member within the female member. The connector is used principally to facilitate storage and shipping.
U.S. Pat. No. 4,564,177 is directed to an attachment clamp which not only attaches the non-beaded bellows to the piston plate, but also attaches the piston plate to the support structure through a threadable engagement between the clamp and the support structure itself. The bellows herein is attached to the piston by interposing the bellows between the clamp and the piston in a clamping arrangement.
U.S. Pat. No. 4,804,303 discloses an attachment block assembly that is connected to a support structure by use of resilient leg elements. A base component is forcibly removed from the frame plate by flexing the resilient legs inwardly so that a latch member will be allowed to glide over the edge of an opening. Snap fastener legs each have a cam surface to facilitate removal and insertion of the fastener from a plate.
U.S. Pat. No. 4,739,543 discloses a push pin fastener for securing automotive trim to an automobile body. The fastener includes arms or legs having locking surfaces which facilitate insertion of the pin and prevent removal once inserted.
U.S. Pat. No. 4,798,369 discloses an ultrasonic air spring system adapted to be mounted on a vehicle for observing road shock exerted on the vehicle and for maintaining the vehicle body level with respect to the axles.
U.S. Pat. No. 5,005,265 discloses a two-piece stud assembly in which the stud has a plurality of angled flexible camming members engaged within a counterbore receiving aperture of a second member for securing the stud within the bushing for attaching two members together.
U.S. Pat. No. 5,039,124 discloses a frame and suspension assembly which includes an air spring attached between two spaced apart members one being the vehicle frame, the other being the walking member, with the air spring interposed therebetween being connected to each member via a bolt traveling through a mounting plate attached to each member and threadably engaging the piston and end cap of the air spring unit.
Although many of the prior art snap mounting attachment devices perform satisfactorily for the purpose intended, they would not be suitable for mounting air springs between two spaced apart members since they do not provide the necessary rigidity, as well as the necessary strength to resist both axial forces as well as shear forces upon the unit. This lack of strength is evidenced by the fact that the industry does not employ the prior art snap-fit clamps to retain the air springs, but instead provides for studs protruding from both the end cap as well as from the piston to threadably engage, or frictionally engage the spaced apart members. Such studs provide logistical problems in that often the spring is positioned in such a manner that tools cannot be used to tighten nuts onto the studs, and occasionally even the studs themselves prevent the mechanic from easily positioning the air spring between the spaced apart members due to the overall length of the air spring. Moreover, the metal studs are subject to corrosion, and the air spring itself must often be replaced when the studs are broken.
Therefore, the need exists for an improved attachment device which permits the assembly of an air spring between spaced apart members, in areas where accessibility to the mounting surfaces is limited, and in which the attachment device is able to withstand radial shear forces as well as axial forces without loosening or disengagement of the two attached members, and which provides for a durable, long lasting attachment device unknown heretofore in the art.